AN IMPROVED ZOOM LENS FOR CAMERAS

摘要

1. A camera zoom lens having fized lens groups and at least two relatively movable lens groups in which there is provided; either; means for generating a first information signal which determines the rate and direction of movement of the first movable lens group (4) and computing circuit means for computing a target value of X (68) for the position to which the first movable lens group should move, depending on the last computed X and the rate of change of X (as determined by the value of the first information signal); or, means for generating a fixed first information signal the value of which corresponds to the final position required of the first movable lens group.
Means is provided for generating a second information signal whose value determines a relationship between the position of the first movable lens group (4) and the position of the second movable lens (6) group and which thereby controls the overall focal length of the lens groups and signal storage means (72) is provided for storing the computed target value of X for a given period of time or for storing the fixed value of X corresponding to the final position required of the first movable lens group. Further means, responsive to the target (or fixed) value of X and the value of the second information signal, for computing a correction signal (80) dY is provided which when combined with the signal Y will produce an output signal whose value determines the position to which the second movable lens group (6) must move so that the lens will produce an in-focus image of an object at a distance (less than infinity) determined by the selected value of the second information signal;
A central processor (34) responsive to the stored values of X and YR and to information signals relating to the actual positions of the first and second movable lens groups, produces error signals ex and ey corresponding to any discrepancy between the actual positions of the movable lens groups and the target values X and YR for those groups, and velocity servo control systems (14, 16) responsive to the two error signals control the rate of movement and direction of movement (18, 20) of the first and second movable lens groups, depending on the values of the error signals ex and ey respectively.